(a) Field of the Invention
This disclosure relates to a graphene oxide-ceramic hybrid coating layer and a method for preparing the same.
(b) Description of the Related Art
Graphene oxide (or graphite oxide, hereinafter GO) is a sheet-shaped carbon material prepared by acid treatment of graphite, and has a substantial amount of a hydrophilic functional group, for example, a carboxyl group (—COOH), a hydroxyl group (—OH), and the like, on the surface. The surface oxidizing groups produced through an acid treatment process naturally produce hydrogen bonds with water (H2) and thus the GO prepared by such process is hydrated or in a form of a water-containing slurry state. In general, a solid content of the slurry is about 2 to 8 wt % without further treatments.
When the GO is appropriately included in a film or a structure, it provides improved strength and suitable thermal conductivity. However, a treatment that removes contained moisture may deteriorate such properties. In general, GO may be prepared in a form of graphene through a chemical reduction method (e.g., a hydrazine treatment and the like) and a thermal reduction method. Hereafter, the reduced graphene is particularly referred to be as reduced graphene oxide (RGO).
It is evidenced that at least a part of the oxidizing groups on the RGO surface is not thoroughly removed. Generally, an oxygen content of the surface oxidizing groups is less than or equal to about 5 wt % of total carbon backbone content. Thus, the graphene oxide (RGO) of the present invention has an oxygen content of less than or equal to about 5 wt % of total carbon backcone content as being consistent with the oxygen content of the surface oxidizing group.
A heterogeneous mixture of GO or RGO and conventional materials has been recently highlighted which may provide synergic effects of conventional materials and eliminate limitations of those. The heterogeneous mixture may be used for a high strength composite material and a fuel cell. Various developed technologies include, a graphene-nanowire (e.g., semiconductor) hybrid structure where light energy is absorbed in a graphene conductive part and electron-hole pairs are generated, a hybrid composite manufacturing method including graphene sheet/carbon nanotube/a polymer nanoparticle, a method of manufacturing a positive electrode graphene material for a lithium rechargeable battery that is a hybrid material formed by adding an iron (Fe) precursor and a phosphate (PO4) precursor, a method of manufacturing a graphene composite calcinated body having an improved charge and discharge ratio by sintering graphene and a metal oxide particle in air, a method of manufacturing a graphene-titanium dioxide (TiO2) hybrid material by mixing a TiO2 nanopowder with graphene at a high temperature and high pressure and reacting them.
Therefore, with the recent needs for the heterogeneous GO coating materials, the present invention provides a coating sol solution for forming a GO-ceramic hybrid layer having transparency and thermal conductivity using GO and a ceramic.